Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Quantas vezes a fórmula tl 2 ba 2 cuo 6 ocorre?
 ###Tabelas: CREATE TABLE 2000s:_incorporation (2000s:_incorporation_id AUTO_INCREMENT PRIMARY KEY, Season VARCHAR, Competition VARCHAR, Round VARCHAR, Opponent VARCHAR, Series VARCHAR) CREATE TABLE period_of_differently_named_meetings (period_of_differently_named_meetings_id AUTO_INCREMENT PRIMARY KEY, Year INT, Event VARCHAR, Record VARCHAR, Athlete VARCHAR, Nationality VARCHAR) CREATE TABLE "ivy_bridge_quad-core"_22_nm ("ivy_bridge_quad-core"_22_nm_id AUTO_INCREMENT PRIMARY KEY, Model number VARCHAR, sSpec number VARCHAR, Cores VARCHAR, Frequency VARCHAR, Turbo VARCHAR, L2 cache VARCHAR, L3 cache VARCHAR, GPU model VARCHAR, GPU frequency VARCHAR, Socket VARCHAR, I/O bus VARCHAR, Release date VARCHAR, Part number(s) VARCHAR, Release price ( USD ) VARCHAR) CREATE TABLE houston_astros_vs._new_york_mets (houston_astros_vs._new_york_mets_id AUTO_INCREMENT PRIMARY KEY, Game INT, Date VARCHAR, Score VARCHAR, Location VARCHAR, Time VARCHAR, Attendance INT) CREATE TABLE bi-_tl-_and_hg-based_high-__c__superconductors (bi-_tl-_and_hg-based_high-__c__superconductors_id AUTO_INCREMENT PRIMARY KEY, Formula VARCHAR, Notation VARCHAR, T c (K) INT, No. of Cu-O planes in unit cell INT, Crystal structure VARCHAR)  
SELECT No. of Cu-O planes in unit cell FROM bi-_tl-_and_hg-based_high-__c__superconductors WHERE Formula = Tl 2 Ba 2 CuO 6